Physiological Reviews, Vol 76, 299-317, Copyright © 1996 by American Physiological Society
Physiology and biochemistry of Drosophila learning mutants
R. L. Davis
Department of Cell Biology, Baylor College of Medicine, Houston, Texas, USA.
Single gene mutants of Drosophila that are defective in learning/memory
processes have increased substantially our understanding of the physiology,
biochemistry, and anatomy underlying conditioned behaviors. Drosophila
learning mutants can be separated into two general classes, those with
structural defects in the brain and those without (conditioning mutants)
any obvious brain alterations. From studies of brain structural mutants,
two neuroanatomic areas have merged as important for normal conditioned
behavior: the mushroom bodies and the central complex. Biochemical and
molecular genetic studies of the conditioning mutants have implicated
numerous types of molecules in learning, but the adenosine 3',5'-cyclic
monophosphate (cAMP) second messenger pathway has emerged as especially
important. Five different genes in this pathway, amnesiac (a product
similar to adenylate cyclase activating peptides), dunce (cAMP
phosophodiesterase), rutabaga (adenylyl cyclase), DCO (protein kinase A),
and dCREB2 (cAMP-response element binding protein), have proven important
for normal learning. The products of many of these learning mutants are
enriched in mushroom bodies, which highlight the importance of mushroom
bodies for normal learning and the cAMP second messenger cascade for the
physiology of mushroom body cells in their role(s) underlying learning.
Physiological studies of the mutants have demonstrated that plastic
properties of synaptic transmission, including facilitation and posttetanic
potentiation, are abnormal in the mutants. An appendix describing the
currently used paradigms to test Drosophila behavior is included.
